Ultrasonic imaging systems are used to acquire real-time images of the interior of the body by using a transducer incorporating a linear array of piezo-electric elements. Modern imaging systems use a multitude of independent transmitters, each electrically connected to an corresponding piezo-electric element within the transducer. By controlling the phase relationships between the transmit pulses from the multitude of elements, ultrasound energy can be directed to predetermined areas within the body. Similarly, a multitude of independent receivers within the imaging system, each connected to the individual elements of the array, are used to interpret relatively small electrical signals resulting from sound energy impinging on the elements after being reflected from internal structures within the body.
Different transducers are required to fulfill a broad range of diagnostic needs. For instance, small, shallow structures generally are best imaged using a high frequency transducer with a relatively small size. Although this type of transducer inherently provides excellent resolution of the finest details, it has limited ability to view deeper structures within the body. Larger organs, deep within the body, i.e. the heart, are best imaged with lower frequency transducers because of the diminished attenuative losses of low frequency ultrasound energy. These transducers must be relatively small because they must acquire an image through the limited space between the ribs. Obstetric transducers generally are of low frequency but are physically large so that they can get a good view of a large part of the fetus.
One imaging system must support a wide range of transducers. Modern imaging systems use relatively complex programmable digital logic to cause the transducer to transmit ultrasound energy into the body, to receive and interpret the relatively small received signals, and to generate a diagnostically usable image on a display device. Software, customized to the requirements of a particular transducer, must be available to the imaging system to enable it to acquire and display the optimum image for that device. Generally, the current practice is to pre-install the appropriate operating software for each transducer to be used with the imaging system into that system. Thus, before the imaging system can be used, it must determine what transducer will be used; this is generally done by electronically interrogating an identification code that has been factory installed within the transducer. Upon identification of the transducer, it selects from its software library, or archive, the program that is required to support that device. This operating software or micro-code is used to preset programmable logic within the imaging system to parameters optimum for the transducer. Electronic logic controlling the transmitters, the receivers, and the display system are preset during this initialization process.